Synthesis and Properties of Temperature- and Salt-Resistant CP(AM-AMPS-DMDAAC) Nanospheres for Oil Displacement

Polymer nanospheres are commonly used in scientific and industrial fields including petroleum, electronics, and biomedicine. The precise synthesis of polymer nanospheres with a controllable size and regular shape is important for achieving thermal stability and mechanical properties, which will directly affect the oil displacement effect. In this paper, amphoteric CP(AM-AMPS-DMDAAC) nanospheres with a small particle size and regular shape were prepared by using an acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), diallyl dimethylammonium chloride (DMDAAC), and methylene-bis-acrylamide mixed solution as the aqueous phase and Span-80 and Tween-80 as the composite emulsifier, followed by reverse-phase microemulsion polymerization. The results showed that nanospheres had temperature and salt resistance and excellent physical and chemical properties. The thermal decomposition temperature was 236.5 degree celsius, the median size of the particles was close to 50 nm, the swelling factor remained at 6.1 nm/nm after water absorption and expansion in the formation water at 120 degree celsius for 7 days, and the swelling factor was 10.4 nm/nm after 14 days. In addition, nanospheres also exhibit good viscoelasticity and pseudoplasticity. The average plugging rate was 79.5% in the low permeability cores, and after the injection of the CP(AM-AMPS-DMDAAC) nanospheres based on water flooding, the average enhanced recovery rate was 13.46%.